1. Field of the Invention
The present invention relates to a recording and reproducing disk cassette inside of which a recording and reproducing disk, such as a floppy disk, is rotatably supported, and in which the disk is partially exposed through an opening which is normally closed with a shutter plate.
2. Description of the Prior Art
One example of the variety of recording and reproducing disk cassettes known in the art is shown in FIG. 2, wherein a disk 2 is provided in the cassette 1 in such a manner that it may rotate together with a disk hub. A spindle hub extends through an opening in the lower half of the cassette 1 to engage the disk 2 to rotate same. The cassette is provided with an opening 3 exposing the disk 2 such that the disk 2 is brought into contact with a magnetic head. The opening 3 is normally closed by a shutter plate 4 urged by a spring (not shown). During recording and reproducing operation, the shutter plate 4 moves against the force of the spring exposing the disk 2 through the opening 3.
Although movement of the shutter plate 4 is essential, it is undesirable to apply too much force to an outer surface of the cassette 1 since this will reduce the ability of the shutter plate 4 to slide freely. On the other hand, a substantial reduction in the force with which the shutter plate 4 is urged to the outer surface of the cassette 1--while permitting the shutter plate 4 to move easily--may result in the shutter plate 4 (which is provided outside the cassette case 1) floating or moving from the cassette case 1 thus causing the shutter plate 4 to be manually bent, or result in the shutter plate 4 being engaged by other parts of the recording and reproducing device. As a result, the shutter plate 4 will be bent or will not be smoothly moved.